Piston molding apparatus



Dec. 22, 1936 F. N, NUTT 2,065,287

P I STON MOLD ING APPARATUS Dec. 22, 1936.

F. N. NUTT 2,065,287

PISTON MOLDING APPARATUS Filed March 27, 1929 'I Sheets-Sheet 2 PatentedDee. 22, 1936 rls'roN Monouso Arranaros y Frank N. Nutt, Flint, Mich.,assignor, by menne assignments, to General Motors Corporation, Detroit,Mich., a corporation of Delaware Application March 27, 1929, serial No.350,296 zo claims. (Ci. 2er-12s) For well` known reasons, it isdesirable to use `what are commonly known as permanent molds.i. e. moldswhich consist of `a metal body anda metal core-in casting pistons oflight metalsor alloys. And sincepistons of light metals or alloys, aswell, in tact, as pistons oi heavy metals or alloys, are commonlyprovided with a 'plurality o't internal projections, it has heretoforebeen considered necessary to provide such molds with complicated,multipart cores in order that the castings may be separated'irom thecoresatter the'molten metal has congealed. A `core oi this type isobjectionable for the reason. among others, that, due to the irregularshape 154 oifthe several parts, they become warped and,

, consequently, difiicult to manipulate after being subjected to the.temperatures encountered during the casting operation. My inventionresides in the provision of cer- `tain new and useful improvements inmolding apparatus for use" in casting pistons, particularly pistons madeof light metals or alloys, and particularly, in apparatus of the typedescribed, in the provision of a mold which includes a mold body made ofan inirangible material, suchV as iron or steel, and a core of which theportions which can be withdrawn as a unit from the casting alter themolten metal has congealed,"without iracturing the casting. are made ofan ,ini'rangible material, such as iron or steel, and the portions whichcannot be withdrawn from the casting. without iracturing `it for them orwithout'being moved with respect to the ilrst-mentioned portions. aremadeof a suitable `frangible material, such as molding sand, plaster ofParis, A or suitable graphite compositions. 1

V `In the accompanying drawings there are illustratedpreierredembodiments of my invention,

for a 4detailed description oi4 which reference made to the followingspeciiication.

In thedrawings; Figure 1 A-is a view showing,mainly in vertical crosssection, piston molding apparatus, in which is embodied my invention;with the parts in positionto receive the moltenmetal oi which the pisitoncasting is to be made. i Figure 2 is a view, similar to Figure 1. butshowing'the parts of the molding apparatus `in the positions which theyoccupyafter thecore has been lowered and thehalves of the mold body havebeen'moved to an intermediate position preparatory to removing a castingtherefrom. -Figure 3 is an end elevation of the molding apparatus shownin the preceding figures with the' with, there extends a cylindricalopening 22. On

parts in the same positions in which they are shown in Figure 1.

" Figure 4 is an enlarged fragmentary view showing the coreand one sideof the mold body of the molding apparatus shown in the preceding 5 guresin section on-the line 4 4 of Figure 6.

. Figure 5 is an exploded side elevation of the Vcore o! the moldingapparatus shown in the preceding ilgures.

Figure 6 is a top planview of thecore o! the 10 molding apparatus shownin the precedi gures. I

`Figure '1 is a fragmentary side elevation, with parts broken away andin section, of aslightly modiiied form oi core. 15

Figure 8 is a top plan-view of the core shown in Figure '1.v

, Figure 9 is a fragmentary section taken on the line 9-9 oi Figure` 8.

Figure 10 is a view, partly in side elevation and partly in longitudinal`cross section through the axis of the wrist pin bosses, of a completedpiston oi the type which` the apparatus shown in the precedingilguresisdesigned to produce.

' Figure 11 is aV section taken on line Ii-Ii of u Figure 10.

The i piston, which the i molding" apparatus shown in the drawings isdesigned to produce is shown, as it appears after having been machinedand ilnished. in vFigures 10 and 11 of the draw- 30 ings. The lpiston ismade of a light aluminum alloy and consists of a head a and a skirt b.In the upper end oi the skirt is embedded a ring c of a `metal or alloy,such as iron, steel, or invar metal, which has a lower temperaturecoefficient 35 of expansion than the aluminum alloy of which the pistonis made. From diametrically opposite webs d formed integrally with theskirt and partially separated thereirom by upper and lower arcuate slotse and f extend inwardly projecting 4o wrist pin bosses y'. Columns h,integral with the wrist pin bosses and the head oi' the piston, extendvertically upward from the inner ends of the wrist pin bosses to the endwall oi the head and are separated `from the side walls of the 45 headand the skirt by spaces i.

'The molding apparatus shown in the drawings includes 4a support 2lthrough which.and a depending guide member 2| formed integral there- 50the upper surface of the support and on opposite sides of the opening 22are provided guideways 2 3. In each of the guideways' 23. there ismounted to slide toward" and away from the opening n 22 a frame 24 whichcarries a half of the mold body.

Each half of the mold body is made of a suitable infrangible material,such as iron or steel, and consists of a wall 28 in which is provided asubstantially semi-cylindrical recess whose upper end is closed by awall 21 in the diametral edge of which is formed half oi the pouringgate 2l. The interior surfaces of the walls 23 and 21 are so shapedthat, when the halv of the mold body are in their innermost positions,in which the side and top walls of one abut against the side and topwalls, respectively, of the other, as shown in Figure 1, there is formedtherebetween a cavity which is coaxial with the opening 22 and whosewalls are so shaped as to give the desired form to the outer side andend walls of the piston casting and to provide cores 29 for the wristpin boss cavities.

To give the desired shape to the interior of the piston casting. thereis provided, as shown in Figures 1 to 6 of the drawings, a core 30 onwhich is provided a cylindrical guide extension 3| which is slidablymounted in the guide member 2|. The core is of such shape as to give thedesired form to the interior of the piston casting and, with theexception of the portions 32 which are adapted to core the spaces ibetween the columns h and the adjacent portions of the inner side wallof the casting, is formed of av suitable infrangible material, such asiron or steel. The portions 32, which may be made of any suitablefrangible material, such as molding sand, plaster of Paris, or asuitable graphite composition, are generally arcuate in shape, areadapted to fit into recesses 33 formed in the sides of the infrangibleportion of the core by removing the portions thereof directly above thewrist pin boss cavities, and are provided with lateral extensions 34adapted to ilt into the undercut portions of the recesses 33 tointerlock the portions 32 with the infrangible portion of the core.

In the event that it is desired to incorporate in the skirt of thepiston a ring, such as c to control the expansion and contractionthereof, there are provided on the infrangible portion of the coreprojections 35, each spaced 90 from the axis of the wrist pin bosscavities and diametrically opposite each other, on which the ring isadapted to be supported during the casting operation. In this event itmay also be advisable, as shown in the drawings, to form each of thefrangible portions of the core in two parts, 33 and 31, whose plane ofseparation is perpendicular to the longitudinal axisof the casting andat the level of the center of the ring c, to form on the parts 36projections 33 having in their upper surfaces substantiallysemi-cylindrical recesses 39 in which diametrically opposite portions ofthe ring c are adapted to be seated and which are adapted to provideadditional support for the ring during the casting operation, and toform on the parts 31 projections 40, adapted to be seated on the uppersurfaces of the projections 38 and having therein substantiallysemi-cylindrical recesses 4| adapted to receive diametrically oppositeportions of the upper half of the ring.

There may be formed, as shown in the drawings, on the parts 38 of thefrangible portions of the core, arcuate ribs 43 to core the arcuateslots e which partially separate the webs d from the skirt b oi thepiston. If, for any reason, it is undesirable to provide these coreportions on the frangible portions of the core, they may be formed onthe interior surface of the mold body.

In Figure 1, the parts of the molding apparatus are shown in thepositions which they occupy when the mold is ready to receive the moltenmetal from which the casting is to be made. The molten metal isintroduced into the interior of the mold through the gate 28 and flowsinto and 1111s all of the space between the mold body and the core andthus produces a casting of the desired shape. It will be noted thatduring this operation, molten metal is introduced directly into thewrist pin boss cavities from the gate 23 through the portions of therecesses 33 which are located between the infrangible and frangibleDOrtions of the core.

To separate the halves of the mold body, after the molten metal hascongealed, so that the casting may be removed therefrom, there isprovided on the support 20, adjacent the outer end of each of theguideways 23, a bracket 44 in which is journalled a shaft 45. To each ofthe shafts 45 is secured an operating arm 46 and a pair of cranks 41.Between each pair of the cranks 41 is pivotally secured one end of alink 48 which is bifurcated at its opposite end and carries adjacent thelatter end a pin 49 which extends between its legs and is adapted to beseated in any one of a plurality of notches 50 which are provided in theupper surface of the frame 24.

To separate the halves of the mold body, the pins 49 are each seated inone of the outer notches 50 (as shown in Figure l) and the upper ends ofthe levers 46 then swung outwardly to the positions in which they areshown in Figure 2. After this, the upper ends of the levers 45 may beswung inwardly until the pins 49 engage in the inner notches 50 and thenagain swung outwardly until the halves of the mold body are entirelyclear of the casting. It is obvious that, under ordinary conditions, thepreliminary separating operation may be dispensed with and the halves ofthe body moved to positions in which they are entirely clear of thecasting by a single operation.

To maintain the core 30 in its uppermost position, in which it is shownin Figure 1, there is provided a spring catch 5| which is secured to theguide member 2| and is adapted to engage a boss 52 formed on the lowerextremity of the guide extension 3| of' the core. To move the core fromits uppermost to its lowermost position and vice versa, there isprovided on each side of the guide member 2| a toggle linkage whichconsists of pivotally connected links 53 and 54 which are pivoted,respectively, to the guide member 2| and the guide extension 3|. Thelinks 53 are provided with extensions 55 which serve as operating armsfor the toggle linkages and which are secured together adjacent theirfree ends so that the two toggle linkages may be operated as one.

After the halves of the mold body have been moved to positions in whichthey are entirely clear of the casting, the arm 55 is operated to movethe core 30 downwardly from the position in which it is shown in Figure1 to that in which it is shown in Figure 2. Since the casting cannotmove downwardly with the core and the frangible portions 32 of the coreare interlocked with the casting, the downward movement of the core willfree the infrangible portion thereof from the casting and separate itfrom the frangible portions 32. The casting may then be removed from themolding apparatus by lifting it vertically. The separation of thefrangible and infrangible parts of Vthe core may fracture and free theformer from the casting but if it does not this may be done by u acostarcore in the recesses 33 in an infrangible portion of the core. (3) toseat the ring c on the projections 35 and in the recesses 3d in theprojections 38. (4) to insert the upper parts 3l or the frangibleportion o1' the core in the recesses 33 in the infrangibleportion oi.the core, and (5) to move the halves of the mold body back to thepositions in which they are shown in Figure 1.

The modified `form of `core which is shown in Figures 'l to 9 of thedrawings differs from that shown in the preceding figures only (1) inthat, instead of two arcuate lower frangible core parts there isprovided a single annular frangible core part 56, which may be describedas consisting of two parts, similar to those which are designated by thereference characters 36 in the preceding gures, arranged diametricallyopposite each other and integrally joined by two arcuate sections, oneach of which is formed at 90 to either of the projections 5l, which aresimilar to and correspond to the projections 38 shown in the precedingflgures,`projections 58 which replace and perform the same functions asthe parts 35 shown in the preceding figures; (2) in that, instead of twoarcuate upper frangible core parts, there is provided a single annularfrangible core part 59, which may be described as consisting 'of twoparts, similar to those which are designated by the reference characters3l in the preceding gures, arrangedy diametrically opposite `each otherand integrally joined by two arcuate sections; and (3) in that theinfrangible portion Gil of the core is cut away to provide arcuaterabbets 6i, which communicate with the recesses 62, which correspond tothe recesses'which are designatedby the reference characters 33 in thepreceding figures, and which are provided to receive the additionalsections, hereinbefore mentioned, of the frangible core parts 56 and 59.The method of assembling the frangible core parts 56 and 59 and the ring`c on the infrangible core part previous to each casting operation willbe obvious from what has previously been said regarding thecorresponding parts shown in the preceding iigures. `'Ihe advantage ofthe structure shown in Figures 'l to 9 over that shown in the precedingfigures is that there are only half the numberof frangible core parts tobe assembled on the infrangible core part previous to each castingoperation.

It will be understood that, although I have described `the moldingapparatus in which is embodied my invention as adapted for use incasting pistons of light metals or alloys, it may be used in castingpistons of the heavier metals or alloys; that the upper and lowerfrangible core parts, which have been shown and described as separatepieces, may be made integral; and that many the type in which the skirtis connected to the head by columns spaced inwardly from portions of theside walls of the piston, a mold body, and a core having therein columncavities the walls of which are formed in part by a irangible materialand in part by an infrangible material.

2. In apparatus for use in molding pistons of the type in which thereare provided on the shirt i inwardly projecting wrist pin bosses and inwhich the head is connected to the shirt hy columns which extend fromthe inner ends or the wrist pin bosses to the end wall of the head andwhich are disconnected from the side walls of the skirt and headintermediate the wrist pin bosses and the end wall of the head, a moldbody, and a core having therein wrist pin boss cavities, and columncavities. the inner walls of which are formed of an infrangible materialand the outer walls of which are formed of a frangible material, andeach of which extends from the upper end of the core and communicates atits lower end with one of the wrist pin boss cavities.

3. In apparatus for use in molding pistons, a

`mold body formed of an infrangible material, and

a core on which there is provided a casting engaging surface of which aportion is formed of an infrangible material and a portion of afrangible material.

4. Apparatus for use in molding pistons which includes, a mold bodyonwhich there is provided a casting engaging surface, and a core onwhich there is provided a casting engaging surface, one of said surfacesbeing formed in part of an infrangible material and in part of afrangible material, and the other of said surfaces being formed in wholeof an infrangible material.

5. In apparatus for use in molding pistons, a mold body, a core of whicha portion is formed of an infrangible material and a portion of afrangible material, and means to move the infrangible portion of theucore with respect to the casting in order to fracture the irangibleportion of the core and free the casting from the core.

6. In apparatus for use in molding pistons, a mold body which consistsof a plurality of relatively movable parts which are made of aninfrangible material, a core of which a portion is formed of aninfrangible material and a portion of a frangible material, means tomove the several parts of the mold body with respect to each other andthe casting to free said parts from the casting, and means to move theinirangible portion of the core with respect to thecasting in order tofracture the frangible portion ofthe core and free the casting from thecore.

'7. In apparatus for use in molding pistons, a

mold bodyyand a core which includes portions which are adapted to beinterlocked with the casting so that they cannot be withdrawn therefromby simply moving them axially of the casting, and other portions whichcan be withdrawn from the casting by simply moving them axiallythereof-the iirst mentioned portions being made of frangible materialand the last mentioned portions being made oi.' lnfrangible material.

8. In apparatus `for use in molding pistons, a mold body, and a core inwhich there are provided wrist pin boss cavities-portions of the coreabove the wrist pin boss cavities being made of a frangible material,and the remaining portions of the core being made of aninfrangible'material.

9. In a core for use in molding pistons, a body made oi an inirangiblematerial having therein wrist pin boss cavities, and recesses extendingfrom the wrist pin boss cavities to the head end therecesses.

10. In a core for use in molding pistons, a body in which there isprovided a projection cavitythe portions of the body below theprojection cavity being made of an infrangible material and portionsabove the projection cavity being made of a frangible material.

11. In a core for use in molding pistons, a body made of an infrangiblematerial and having in the side walls thereof wrist pin boss cavitiesand recesses having undercut portions extending from the wrist pin bosscavities to the head end thereof. and inserts of a frangible material inthe recesses and having portions engaged in the undercut portionsthereof to interlock the inserts with the body of the core.

12. In apparatus for use in molding pistons of the type in which thereis embedded in the side wall thereof a metallic ring, a mold body, and acore on which there are provided projections on which the ring isadapted to be supported during the casting process.

13. In apparatus for Vuse in molding pistons of the type in which thereis embedded in the side wall thereof a metallic ring, a mold body, and acore of which portions are made of an infranglble material and portionsof a frangible material, and projections on which the ring is adapted tobe supported during the casting process, of which projections one isformed on an infrangible portion and another on a frangible portion ofthe core.

14. In apparatus for use in molding pistons, a core made of aninfrangible material and in the outer side wall of which is provided avertically extending recess having undercut portions, and upper andlower segment-like inserts in said recess and having portions engaged inthe undercut portions of the recess to lock the inserts in the recesses.

15. In apparatus for use in molding pistons, a

' core made of an infrangible material and having in the outer side wallthereof an annular recess and a ring-like element of frangible ma'terial seated in the recess.

16. In apparatus for use in molding pistons of the type in which thereis embedded in the side wall thereof a metallic ring, a mold body, acore made of an infrangible material and having in the outer side wallthereof 'an annular recess and a ring-like element of frangible materialseated in the recess and having thereon projections on which the ring isadapted to be supported during the casting process.

17. A core for cup-shape articles having an internal undercut comprisinga permanent centrai section and two disintegrable side sections, thecentral section comprising the entire core outside the undercut portionsof the casting and the central part of the core at the undercut portionsof the casting.

18. A core for cup-shape articles having an internal undercut comprisinga permanent section forming the entire core outside the undercut portionof the article and having a reduced axial extension forming the centralpart of the core at the undercut portion of the article and twodisintegrable core sections having a shape complemental to the undercutportion of the article and detachably'secured to the axial extension onsaid ilrst section.

19. A core for cup-shape articles having an internal undercut comprisinga permanent section forming the entire core below the undercut 2,065,987of the core, and inserts of frangible material in.

portion of the article and having a longitudinal extension forming thecentral part of the remainder of the core, and two disintegrablesections for forming the undercut recesses in thev article detachablysecured to the extension on said permanent section. the contiguous facesof the sections having dove-tail interlocking relation.

20. Molding apparatus comprising a permanent mold having a castingcavity therein shaped to form the outer walls of a piston, a permanentcorevconstruction removably positioned within said casting cavity andspaced from the walls thereof to define the inner surface of the pistonskirt and a pair of oppositely disposed piston pin bosses, saidpermanent core construction extending toward said mold to form a portionof the under surface of the piston head and being widely spaced from theside walls of said casting cavity between the piston pin bosses and thehead to form the inner surfaceseof a pair of webs extending from thehead to the bosses, and a pair of oppositely disposed cores spaced fromsaid mold and from said permanent core construction to define portionsof the inner surface of the piston and the outer walls of the webs.

2i. Molding apparatus comprising a permanent mold having a substantiallycylindrical casting cavity therein to form the outer walls of a piston,positioned within said casting cavity and having a substantiallycylindrical portion spaced from said mold to define the inner surface ofa portion of the piston skirt, said permanent core construction beingoffset inwardly on opposite sides to define the inner surfaces of a pairof piston pin bosses and a web integral with one of said piston pinbosses, and a sand core spaced from said mold to deiine the innersurface of a portion oi' the cylindrical wall of the piston and spacedfrom said permanent core construction to define the outer wall of theweb.

22. Molding apparatus comprising a permanent mold having a castingcavity therein shaped to form the outer walls of a piston, a permanentcore construction removably positioned within said casting cavity andspaced from the walls thereof to define the inner surface of the pistonskirt and a pair of oppositely disposed piston pin bosses, saidpermanent core construction extending toward said mold to form a portionof the under surface of the piston head and being widely spaced from thesidewalls of said casting cavity between the piston pin bosses and thehead to form the inner surfaces of a pair of webs extending from thehead to the bosses, and a pair of oppositely disposed sand cores spacedfrom said mold to denne portions of the inner surface of the piston andspaced from said permanent core construction to define the outer wallsof the Webs.

23. Molding apparatus comprising a permanent a permanent coreconstruction removably mold having a substantially cylindrical castingvI cavity therein to form the outer walls of a piston, a permanent coreconstruction removably positioned within said casting cavity and havinga substantially cylindrical portion spaced from said mold to denne theinner surface of a portion of the piston skirt, said permanent coreconstruction being on'set inwardly on opposite sides to define the innersurfaces of a pair of piston pin bosses and a pair of webs integral withsaid bosses, and a pair of sand cores spaced from said mold to deiinethe inner surfaces of portions of the cylindrical wall oi the piston andspaced fromA said permanent core construction to define the outer wallsof the Webs.

2li. A piston mold comprising a permanent mold having a substantiallycylindrical casting cavity, a permanent core member supported withinsaid casting cavity and spaced from said mold to define the innersurface of the piston skirt, oppositeiy disposed inwardly projectingpiston pin bosses and webs extending from the bosses to the head of thepiston, and a pair of sand cores spaced from said permanent core to denethe outer surfaces of the webs between the bosses and the head, andspaced from said mold to define a portion of the inner surface of thewall of the piston.

25. A piston mold comprising -a permanent mold having a substantiallycylindrical casting cavity therein shaped to form the 'outer Walls ofthe head and skirt of a piston, a permanent core construction removablysupported in said casting cavity and h-aving a substantially cylindricalportion spaced from said mold to define the inner surface of the pistonskirt and a reduced extension for defining the inner surfaces of a pairof piston pin bosses, said reduced extension being continued to form thecentral portion of the inner surface of the head, and a pair ofnonp-ermanent cores arranged between the bosses and the head on oppositesides of said reduced extension.

26. Molding apparatus comprising a permanent mold having a castingcavity therein shaped to form the outer walls of a piston, a permanentcore construction removably positioned within said casting cavity andspaced from the walls thereof to defme the inner surfaces of the pistonskirt at the open end thereof, the sides of said core construction beingoffset inwardly to form the inner surfaces of a. pair of piston pinbosses and the inner surfaces of `webs extending from said piston pinbosses to the skirt, the offset portion of said core construction beingextended to form a portion of the inner surface of the piston head andto form the inner walls of a pair of hangers extending from said pistonpin bosses to the head and a pair of sand cores arranged to providere-entrant recesses between each of the sand cores and the permanentcore to form the outer side surfaces of the hangers and the adjacentinner surfaces of the piston skirt and head. l

27. Molding apparatus comprising a permanent mold having a castingcavity therein shaped to form the outer walls of a piston, a permanentcore construction removably positioned within said casting cavity andspaced from the walls thereof to define the inner surfaces of the pistonskirt at the open end thereof, the sides of said core construction beingoffset inwardly to form the inner surfaces of a pair of piston pinbosses and the inner surfaces of webs extending from said piston pinbosses to the skirt, the offset portion of said core construction beingextended to form a portion of the inner surface of the piston head andto form the inner walls of a pair of hangers extending from said pistonpin bosses to the head and a pair of sand cores arranged to providere-entrant recesses between each sand core and the permanent core so asto form the outer side surfaces of the hangers and the adjacent innersurfaces of the piston skirt and head, said sand cores being supportedby said permanent core construction.

28. An internal mold for use in casting a piston with integral wrist pinbosses, consisting of a metallic core conforming to a portion of theinterior of the piston with a plastic mold material associated with saidcore to form portions of the interior of the head of the piston and thewrist pin bosses.

29. A combination core for a piston for internal combustion engines,consisting of a metal core substantially conforming to the interior ofthe body element and a portion of the head element of the piston, and aplastic mold insert associated with said metal core to complete theformation of said combination core.

FRANK' N. NUTT.

